Connectors for optical fiber transmission systems are known in the art. Often times it becomes necessary to arrange a plurality of optical fiber connectors in a panel to facilitate multifiber connections. Desirably, devices for holding connectors are mounted in the panel but the connectors themselves are not connected to incoming or outgoing fiber paths until needed to provide service. Devices which are mounted in a wiring panel to accommodate interconnections commonly are referred to as buildout blocks and buildouts.
A very much used ferrule connector for terminating and connecting two optical fibers is one which is referred to as an ST.RTM. connector, ST being a registered trademark of AT&T. The ST connector is disclosed, for example, in U.S. Pat. No. 4,934,785 which issued on June 19, 1990 in the names of T. D. Mathis and Calvin M. Miller.
An ST connector includes a cylindrical plug or ferrule, as it is often called, having a passageway therethrough for receiving an end portion of an optical fiber to be terminated. The plug which is received in a cap is spring-loaded. When two of the plugs are received end-to-end in a coupling sleeve, for example, one or both of the plug bodies is moved along its longitudinal axis during the connection process.
There are a number of concerns which must be addressed by optical connection arrangements. It is well known to use connector adapters in panels to receive connectors. Connector adapters as well as buildout blocks may be received in panels to accommodate connectors to be installed at a future time. The capability should exist for connecting a first connector which terminates an incoming or outgoing fiber path to a buildout block to await future connection of a second connector which terminates an outgoing or incoming fiber path. It is desired to provide those kinds of arrangements with the expensive portions such as connector adapters or buildouts installed when needed for customer service.
Buildout blocks in an optical wiring panel may number in the hundreds or even thousands. With close spacing between adjacent ones in order to conserve space, it becomes difficult to perform installation, replacement or connection steps on the connector adapters or buildout blocks at the rear of panel, or for that matter, in the front of the panel.
Also, often attenuators are needed in the transmission path to reduce the strength of an incoming signal to a required level. Many optical fiber communication systems require a method of decreasing optical power at a reducing station to avoid the saturation of receivers. Such a reduction in power may be accomplished by introducing into the system a device known as an attenuator which is designed to dissipate or to attenuate a controlled fraction of the input power while allowing the balance to continue through the system. Such an attenuator is disclosed in application Ser. No. 07/566,588 filed on Aug. 13, 1990 in the names of R. R. Cammons, A. W. Carlisle and N. R. Lampert.
Changing of the attenuation level also may be required. It is known that the efficiency of a circuit decreases with age and that the power of a signal source which may be adequate at the beginning of life of a circuit later may become inadequate. If the power of the signal at the beginning is chosen so that it remains adequate later, components of the circuit may become saturated early in life. Additionally, the unearthing of cable which results in repairs that add optical loss to the transmission path can be compensated for with a lower loss attenuator. Often times, the required attenuation is introduced at an optical wiring panel or at an optical backplane where it is most convenient to insert an attenuator between connectors.
Another problem in arriving at an interconnection arrangement having the sought-after features is that during the connection process for the ST connector, as mentioned hereinbefore, movement occurs in a plug which is first inserted into a coupling sleeve when another plug is inserted into the sleeve. Any widely accepted attenuator system must be able to accommodate such movement.
Complicating matters for arranging cylindrical ferrule connections which may include attenuating provisions is the recognition that there is no universally accepted ferrule connector. AT&T's ST connector is used widely, as is a Japanese-based connector referred to as the FC connector. Desirably, a sought-after interconnection arrangement may be used to accommodate both connectors. What is needed and what does not seem to be available is a buildout interconnection arrangement which may be used in single mode-to-single mode ferrule connecting arrangements, such as for example, an ST connector-to-an ST connector or an ST connector-to-an FC connector.
What also is sought and what does not appear to be available in the prior art is a ferrule connector arrangement for wiring panels which may include an in-line buildout attenuator which results in low reflected power. Desirably, the sought after attenuator may be integrated easily and be compatible with existing ST and FC connection systems.
Further, it would be desirable to have a buildout provided with an attenuator element which may be assembled simply to a buildout block already in the wiring panel. This avoids an investment in apparatus before the time when a fiber path is put into service, yet provides an organized and relatively, inexpensive arrangement for storage of connector plugs which are mounted in buildout blocks when the buildout blocks are mounted in a panel.
Such a system of buildouts and buildout blocks for ferrule connectors desirably should be one which is capable of accommodating FC connectors as well as ST connectors. Further, the system should be one for which the decision as to which ferrule connector to use may be postponed, if necessary, until the time that service is required on a particular fiber path or paths. Also sought after is a buildout system for which manual manipulations may be performed from a front face of an optical wiring panel without special tools so that for each fiber path, a plug terminating one side of the fiber path can be connected easily to a connector already mounted in a buildout block in the panel and connected to the other side of the fiber path. Seemingly, such a buildout system is not available in prior art.